Oceanography.....covers a wide range of topics, including marine organisms and ecosystem dynamics; ocean currents, waves, and geophysical fluid dynamics; plate tectonics and the geology of the sea floor;

Marine geology is the study of sediment cores, mainly in the Ocean Drilling Program. to measure numerous proxies and try to make sense of it. See also this.

In my very personal opinion, accumulated over the years, it's the most misunderstood part of Earth science.